Wiring a Panel

Wiring a Panel – EPIC Style

This page describes the method I use to organize the wiring of a a panel. The principle is the same both for a simple panel containing only buttons and for a more complex one with buttons, LED’s or rotaries.

EPIC works with a matrix consisting of 8 data leads and a total of 38 rows (on three modules). This allows for a maximum of 304 buttons. Each button should be protected by a diode. I found it impractical to solder the diodes directly to the contacts of the buttons or switches. As an alternative, I route all ModRow leads and all data leads from the panel to a small connector board. This board holds all diodes, and here is where the organization of cables takes place.

The board is located between the panel and the DB25 connector – which is plugged into one of the distribution boards for further connection to the EPIC modules. The series of photos that follows illustrate the steps necessary to make the connector board.

The fully wired panel. 8 buttons can be wired to the same ModRow lead. Note the yellow ModRow cable connecting vaious switches. For rotary switches, the ModRow lead must be soldered to the central (common) contact.

Note the sheet of paper where all button asignments are noted. It is very important to keep track of all wiring. It might all be so clear today – be sure that tomorrow you will be consulting your notes to track cables and the buttons or switches they go to!

First step in the process of making the connector card is to solder the diodes. For clarity’s sake, I always put groups of 8 diodes in a row, representing the 8 data leads. Each of these groups corresponds to 1 ModRow. If not all 8 data leads are used in a group, there is obviously no need to put all 8 diodes – just leave the corresponding space empty. But it is a good idea to stick to the grouping idea. The group in the upper left corner consists only of data leads 1 – 3, the group in the lower left corner of leads 2 – 8. Therefore, the first “slot” is left empty.

Diodes must always be soldered in such a way that the ring on the diode points towards the switch or button.

Backside of the connector board. Note the type of board used. The grouping of 3 contacts allows for easy connection of up to 2 cables on each side of the diode. The side that leads to the switch needs only one, but the other side of the diode is where the data leads are connected. Since in this example more than one ModRow is used, the data leads have to branch into each of the groups of 8 diodes. This concept will become clearer with the next photos.

A male connector for a ribbon cable is added. An adjacent panel with only a few buttons is connected here for simplicity’s sake. The alternative would have been to produce another connector board, cable and DB25 plug.

So, from this point on, both panels will share the same cables and DB25 connector.

The first data lead is soldered in. As noted above, the group of diodes in the lower left corner consists of only 7 diodes, namely #2 to #8. Still, the data lead 1 is connected to the #1 position. The red calbes then branches to all other #1 – data lead positions on the board, in this case 4 (one of them on the adjacent board, as explained above).

More data leads are added. They are color coded, so I hope the concept becomes clear.

It starts to look a bit confusing, but the data leads are now all connected. The wires from the switches and buttons are soldered to the other side of the diodes (the side marked with a black ring).

The finished product! To protect the contacts and avoid short circuits, I wrap the whole board in a sheet of transparent plastic.

Again, it is important to have meaningful documentation about all connections. What you see here is a drawing of the DB25 connector. It contains precise information on each cable soldered there, even including it’s color.

The circuit board is also the only viable solution I can think of, if you decide to employ binary encoded rotaries (or switches) as a way of increasing the number of buttons beyond the 304 normally available in the EPIC environment. I generally do not recommend binary encoding, because it leads to enormos complications both in wiring and programing. But if you need more that 304 buttons, binary encoding is the only alternative to buying another EPIC card and expansion modules.